Electric paper is a re-writable medium that affords the convenience of paper in an electronic medium. In particular, electric paper is usually lightweight, thin and flexible and displays images indefinitely while consuming little or no power. Ideally, electric paper is also reusable and displays images using reflected light and allows a very wide viewing angle.
One form of electric paper is a gyricon system disclosed in various patents and articles such as U.S. Pat. No. 4,126,854 by Sheridon titled “Twisting Ball Display”. The gyricon system includes a host layer a few millimeters thick that is heavily loaded with bichromal elements, possibly spheres, tens of microns in diameter. Each bichromal element has halves of contrasting colors, such as a white half and black half. Each bichromal element also possess an electric dipole, orthogonal to the plane that divides the two colored halves. Each bichromal element is contained in its own cavity filled with a dielectric liquid. Upon application of an electric field, the bichromal elements rotate depending on the polarity of the field presenting one or the other colored half to an observer. Other forms of electric paper include electrophoretic particles (such as U.S. Pat. Nos. 6,829,078 and 5,961,804) and electrochromic medium (such as U.S. Pat. No. 6,587,250).
One way to make electric reusable paper cheaper and enable the use of cheap flexible plastic films in packaging the electric paper is to completely remove the driving electronics from the electric paper. Instead, an “electric paper printer” includes external addressing electronics to write and erase images. This approach reduces the per unit cost of electronic paper sheets. Multiple electronic paper sheets can then be addressed by a single set of external driving electronics, much as multiple sheets of pulp paper are printed on by a single printer. Such a system is described in U.S. Pat. No. 6,456,272 entitled “Field Addressed Displays Using Charge Discharging in Conjunction with Charge Retaining Island Structures” which is hereby incorporated by reference in its entirety.
One problem facing the use of such external electric paper printers is that external addressing devices are limited by the slow response speed of electric paper optical display elements. In example bichromal element electric paper substrates, complete rotation of bichromal elements is achieved when the addressing electric field is maintained for the entire bichromal element rotation time, typically on the order of 400 milliseconds. For a sheet that includes many rows of an image, it could take many seconds or possibly minutes to print the entire image.
Thus a technique for enabling an electric paper printer to more rapidly output electric paper sheets is needed.